Draggers or dragging equipment detectors are used in the railroad industry to detect the presence of objects loosely hanging below a railroad car. Low hanging objects can impact and severely damage switches, tracks, ties, and other equipment placed adjacent and/or between the rails. Low hanging objects also have the potential to derail railroad cars.
One type of detector, known as a static dragging equipment detector, has a plurality of fixed position paddles. Each paddle has one or more force sensors, for example acceleration sensors, to sense a force impact against the paddle. One shortcoming of such detectors is that not much can be ascertained from a force impact except that something hanging low on the train hit one or more paddles.
An exemplary dragging equipment detector is disclosed in U.S. Pat. No. 6,412,332 to Bartonek that issued on Jul. 2, 2002 (“the '332 patent”). Specifically, the '332 patent discloses a dragger that has four impact elements, two located outside of a track and two located inside the track. The '332 patent discloses that each impact element houses a single axis sensor, which is mounted such that it can detect a horizontal component but not a vertical component of any impact forces imparted by objects dragging beneath the train. The '332 patent further discloses that a detection circuit connected to the sensor determines whether the g-force corresponding to the impact exceeds an alarm threshold. Moreover, the '332 patent notes that exclusion of vertical forces avoids the problem of triggering false alarms by detecting vibrations from flat wheels.
Although the '332 patent discloses a static dragging equipment detector with multiple sensors, the sensors of the '332 patent are configured to detect only horizontal impacts. As such the dragging equipment detector of the '332 patent can detect low hanging equipment on a train but cannot detect other fault conditions such as flat wheels or derailment of the train. Additionally, the alarm threshold has a fixed level in the '332 patent. As a result, when a train is moving at a low speed, the impact of low hanging objects on the impact elements may not be detected by the dragging equipment detector of the '332 patent. At high train speeds, the dragging equipment detector of the '332 patent may trigger a false alarm resulting from the impact of spurious objects, for example, icicles, which do not pose a danger to the train or the railroad track.
The dragger of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.